[7.03] The Boron Abundances of 110 Her and 45 Tau

New low noise, HST High Resolution Spectrometer boron B I $\lambda2496$
observations are presented of the F6 subgiant
110 Her and the Hyades F2 dwarf 45 Tau (vB 14). 45 Tau has
previously been shown to have
normal lithium and beryllium abundances for a Hyades F2 star. In contrast,
110 Her is deficient in lithium by more than two orders of
magnitude and in beryllium by roughly a factor
of 10. The effective temperature of 110 Her (6350 K) is
considerably cooler than a
classical Hyades lithium gap star (6600 K).

We show that the surface boron abundance of 110 Her is almost identical to what
is observed in Procyon, used as an empirical
standard. Procyon is known to be deficient in boron by
about a factor of two (Lemke et al.\ 1993, PASP, 105, 468) relative to other
stars of its temperature and composition, and it is
about 0.2 dex more metal-rich than 110 Her.
If initial boron content in Pop.\ I stars
scales with metallicity, then 110 Her
may show an undepleted surface boron abundance.
45 Tau appears to display a somewhat higher
boron abundance, which is presumably unaltered from its
initial, pre-stellar value.
These observations will be compared to predictions of stellar models
which include microscopic diffusion and rotational mixing.